1. Field of the Invention
The present invention relates generally to stator winding and, more particularly, to an apparatus and method for forming wound coils on stator stacks for dynamo-electric machines.
2. Description of the Prior Art
Field winding coils for stators are generally placed on the radially inwardly extending teeth of a stator stack by either pre-forming the coils and then pressing the pre-formed coils over the stator stack teeth, or by winding the coils directly onto the stator stack teeth. In the process where the coils are pre-formed, the coils are pushed onto the stator stack by a coil pusher which forcibly pushes the coils over the teeth of the stator stack, and a forming tool, or forming tools, may be provided to shape the wire in the stator stack slots and around the ends of the teeth in order to compactly position the coils on the stator stack. In such a construction, excess wire must be provided for the pre-formed coils in order to accommodate the necessary distortions of the coils as they are pressed over and around the stator stack teeth. Accordingly, such a construction has been found to provide an inefficient amount of wire, as well as result in a larger stator dimension as a result of the excess coil wire extending around the end faces of the teeth for the stator.
In the alternative construction for field winding, wire is fed from a winding spindle or winding tool directly onto a stator stack wherein the wire is successively wound around the stator stack teeth, and the efficiency of the winding operation is substantially dependent upon the ability to direct the wire to desired locations on the teeth as it is fed from the winding spindle. Such a device for feeding wire onto the stator stack to form the coils directly thereon is disclosed in U.S. Pat. No. 6,616,082.
When the wire being wound into the stator stack slots is of a relatively thick gauge, particular problems arise in the feeding and formation of wire coils on the teeth of the stator stack. In particular, such thick gauge wire does not typically readily conform to the contour of the slot such that the slot fill provided by thick gauge wire may be reduced relative to thinner more flexible gauges of wire.
Further, a winding operation in which pairs of wires are wound into the same slot simultaneously introduces additional difficulties not addressed by prior art machines in that the position of each wire in the pairs of wires must be properly coordinated relative to each other in order to ensure sufficient space for all required windings. The difficulty of providing efficient placement of wires is compounded when multiple sets or pairs of wires are placed in the stator stack simultaneously.
In addition, it has been observed that an additional area for improvement in the winding operation relates to a wire forming operation performed on wire placed within the slots of the stator stack. Specifically, it is known to move a forming tool having radially extending blades into one end of the stator stack for the blades to form the wire toward the respective stator stack teeth around which the wire is wound. For example, the forming tool may be provided with an actuator for moving the forming tool in synchronism with the winding tool. That is, the forming tool may move into the stator stack as the winding tool is moved in a direction out of the stator stack. Typically, an end portion of the winding tool closest to the forming tool remains within or closely adjacent to the end of the stator stack, limiting the ability of the forming tool to approach that end of the stator stack. Accordingly, in such a winding system, at least a portion of the wound wire may not be formed within the stator stack slots.